It’s always been just KDE to me. In the past year or so, I’ve noticed people calling Plasma KDE or even just Plasma. What happened? Why do people insist on making the name longer? Why the word Plasma? What is Plasma referring to? And, are they trying to move away from the KDE name to just Plasma?
Answer: Plasma is the desktop environment. KDE is the community that makes Plasma and many other related software.
Because the “kde” package is a meta-package that has all the utilities of a KDE-install too, while the “plasma” package has only the desktop.